Engineering Materials MCQ Questions & Answers | Mechanical Engineering

The aluminium alloy made by melting aluminium with 2 to 10% magnesium and 1.75% copper is called magnalium

The correct answer is Option A: Ferritic stainless steel.
Let's break down why:

Stainless steels are a family of steels known for their corrosion resistance.
This resistance comes mainly from the presence of chromium (Cr).

There are different types of stainless steel, and they're classified based on their microstructure (the arrangement of atoms within the metal).

* Ferritic stainless steel:
* Contains 12 to 30% chromium and a low amount of carbon (typically less than 0.1%).
* They are magnetic and cannot be hardened by heat treatment.
* The given composition of 16 to 18% chromium and about 0.12% carbon fits this description.

* Austenitic stainless steel:
* Contains chromium (typically 16-26%) and nickel (typically 6-22%).
* Nickel is a key element in Austenitic stainless steel which makes them non-magnetic in nature.
* They are generally more corrosion resistant and easier to weld than ferritic stainless steels.
* The question does not include nickel so it can't be Austenitic stainless steel.

* Martensitic stainless steel:
* Contains chromium (typically 11.5-18%) and a moderate amount of carbon (typically 0.1-1.2%).
* They can be hardened by heat treatment.
* The carbon content in the question is relatively low for a typical martensitic stainless steel.

* Nickel steel:
* This is a general term for steel alloyed with nickel.
* While nickel can improve some properties of steel, it doesn't define the type of stainless steel in this case.

Therefore, a steel with 16 to 18% chromium and about 0.12% carbon is most accurately described as Ferritic stainless steel.

Silicon increases strength and hardness but to a lesser extent than manganese. It is one of the principal deoxidizers used in the making of steels to improve soundness, silicon is detrimental to surface quality, especially in the low carbon, resulphurized grades. It aggravates cracking tendencies when the carbon content is fairly high.

White metal alloys are those which are light-coloured and generally have a lead or tin base. These alloys are known as Babbitt metal
Babbitt metal contains 87.75% Sn, 4% Cu, 8% Sb, 0.25% Bi

Killed steels are those steels Which are deoxidized in the ladle with silicon and aluminium

Pure metals are soft, tough and ductile with a high coefficient of friction. Intermetallic compounds are hard and wear-resistant but brittle. By themselves, these do not make ideal bearing materials.
The white metals are any of several light-colored alloys used as a base for plated silverware, ornaments or novelties, as well as any of several lead-based or tin-based alloys used for things like bearings, jewellery, miniature figures, fusible plugs, some medals and metal type.

Elinvar is a nickel-iron alloy notable for having a modulus of elasticity which does not change much with temperature changes.
Elinvar originally consisted of 52% iron, 36% nickel, and 12% chromium.
It is almost non-magnetic, and corrosion resistant.

In addition to aluminum, the main materials in duralumin are copper, manganese and magnesium.
Although the addition of copper improves strength,
it also makes these alloys susceptible to corrosion.
For sheet products, corrosion resistance can be greatly enhanced by metallurgical bonding of a high-purity aluminium surface layer. These sheets are referred to as alclad, and are commonly used by the aircraft industry

Pearlite is a combination of Ferrite and cementite

Austenite is a combination of Cementite and gamma iron